This application claims the benefit of Japanese Application 2001-052,264, filed Feb. 27, 2001, and Japanese Application 2002-014,076, filed Jan. 23, 2002, the entireties of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a substrate for mounting optical parts, a method of manufacturing the same, and an assembly using the substrate.
2. Description of Related Art
A large number of steps are required when connecting optical parts, since a high degree of precision is needed.
As a means to solve this problem, there has been proposed a method of mounting optical parts on a substrate having guides for mounting optical parts (substrate for mounting optical parts) so as to position relatively the optical parts.
In a collimator array 50 shown in FIG. 10, which is an example of the substrate for mounting optical parts, a groove 52 for securing a fiber and a groove 54 for securing a lens are formed precisely at a relative position. However, in the case where the optical parts to be connected have different diameters, grooves having different sizes must be formed so that the center of a rod lens 15 corresponds to the center of a fiber 16. Therefore, such a substrate cannot be formed by a grinding process in which a passage for a grinding stone is necessary.
As a result, a substrate made of silicon, in which guide grooves for the lens and fiber are formed using anisotropic etching, has been mainly used as the substrate for mounting optical parts.
However, since the silicon substrate for mounting optical parts has a thermal expansion of 2.4xc3x9710xe2x88x926, the difference in thermal expansion between the substrate and the lens (5xe2x88x9210xc3x9710xe2x88x926) used as the optical part is too great. This causes problems such as delamination of the lens due to thermal variation when bonding and securing the lens to the substrate for mounting optical parts.
Moreover, since the silicon substrate does not transmit ultraviolet rays (UV), use of a UV-curable adhesive is limited. Furthermore, the silicon substrate is very brittle, thereby resulting in poor handling capability and the like.
When the silicon substrate is connected to optical parts or mounted in a package, thermal expansion matching with members which the substrate contacts is needed. However, matching is determined in the case of using the silicon substrate and various measures must be taken when using this substrate.
Therefore, use of materials other than silicon such as glass (in particular) for manufacturing the substrates for mounting optical parts has been examined. However, these substrates cannot be subjected to a commonly-used grinding process to form second grooves shown by the reference number 52 in FIG. 10, and, therefore, are manufactured using discharge, ultrasonic machining, or the like. As a result, since the processing dimensional accuracy of these substrates is only about several tens of microns, these substrates cannot be put into practical use.
The present invention has been accomplished in view of the above problems in the conventional art. An object of the present invention is to provide a glass substrate for mounting optical parts excelling in dimensional accuracy, capable of preventing problems caused by the differences in thermal expansion with members, which the substrate contacts, such as optical parts and packages, and capable of improving workability at the time of mounting the optical parts, a method of manufacturing the same, and an assembly using the substrate.
One aspect of the present invention provides a glass substrate for mounting optical parts on which a plurality of optical parts having different diameters is mounted so that the optical parts are specifically positioned, comprising a groove for securing a first optical part having a relatively small diameter among a plurality of optical parts, V-shaped grooves formed on either side of the groove for securing a first optical part, and a groove for securing a second optical part formed so that outer tapered sections of the V-shaped grooves become outer grooves for securing an optical part having a relatively large diameter among a plurality of optical parts.
Another aspect of the present invention provides a method of manufacturing a glass substrate for mounting optical parts on which a plurality of optical parts having different diameters is mounted so that the optical parts are relatively positioned, comprising forming a groove for securing a first optical part, forming V-shaped grooves on either side of the groove for securing a first optical part, and grinding a groove for securing a second optical part while correcting the grinding conditions so that the center of the groove for securing a first optical part corresponds to the center of a virtual groove calculated so that outer tapered sections of the V-shaped grooves become outer grooves of the virtual groove.
The groove for securing a second optical part is preferably formed in a shape whereby only the outer tapered sections are in contact with the optical part having a relatively large diameter and the bottom thereof is not in contact with the optical part.
The groove for securing a second optical part is preferably formed by removing part of the groove for securing a first optical part.
Still another aspect of the present invention provides an assembly comprising the above substrate for mounting optical parts, and a plurality of optical parts mounted on the substrate.
Yet another aspect of the present invention provides a layered assembly in which a plurality of the above assemblies is layered.
Preferably, one of the optical parts mounted on the assembly is a lens, and a step section is formed on the side opposite to the groove for securing an optical part in which the lens is mounted.